The experiments described in the present proposal are designed to investigate age differences in the use of semantic memory information. Subjects' decision time is the primary dependent variable; the additive-factors method and the method of specific effects are the basis of the experimental design and data interpretation. Each experiment employs the lexical decision task, which requires that on every trial subjects decide whether a visually presented letter string (a "target") is a word or a nonword. Previous research with this task has demonstrated that the presentation of a "prime" word immediately prior to the target can reduce decision time, when the prime and target are related words (e.g., BREAD/BUTTER). This faciliation effect apparently occurs because the presentation of the prime activates information in memory that is related to the target word. The proposed experiments will examine the ability of young and elderly individuals to make use of different types of semantic information (defined by specific prime-target relationships) during the lexical decision task. These results will provide a test of Eysenck's "processing-deficit" hypothesis that age-related changes exist in the use of meaning-related information. The experiments will also investigate the time course of the processing faciliation provided by the prime, and will indicate whether age differences are determined by the amount of attentional control required by the task. Finally, the experiments will indicate whether age differences are specifically associated with the memory-retrieval or response-selection stages of the lexical decision task. The results of the project are intended to improve current theories of age-related changes in cognitive function and to have implications for applied and rehabilitative concerns.